Handheld sander

ABSTRACT

A handheld sander includes a main body, an extension arm, a follower draft, and a transmission shaft. The main body includes a housing and a drive shaft rotatably disposed in the housing. The extension arm includes a pivot portion rotatably connected with the housing in a way that the extension arm is rotatable relative to the housing, a distal portion opposite to the pivot portion, and an internal accommodation penetrating through the pivot portion and the distal portion. The follower shaft is rotatably disposed in the distal portion of the extension arm. The transmission mechanism is disposed in the internal accommodation and connected between the drive shaft and the follower shaft for transmitting a rotational power from the drive shaft to the follower shaft. As such, the handheld sander can perform a grinding work in a limit, narrow working space.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates generally to grinding tools and more particularly, to a portable handheld sander.

2. Description of the Related Art

A sander is a tool adapted for grinding or cutting workpieces. The portable handheld sander is extensively used in various working places because the handheld sander can be operated by the user with required angle or orientation in grinding the workpiece. However, when the workpiece under grinding has a specific structural profile or the ambient working space is narrow, the conventional handheld sander may not be able to be operated in such a narrow working space because the conventional handheld sander cannot adjust its structure and has a thick body. In other words, the conventional handheld sander needs to be improved.

SUMMARY OF THE INVENTION

The present invention has been accomplished in view of the above-noted circumstances. It is an objective of the present invention to provide a handheld sander, whose structure and shape can be adjusted in accordance with various working requirements, such that the handheld sander can extend into a narrow working space for grinding processing.

To attain the above-mentioned objective, the present invention provides a handheld sander comprises a main body, an extension arm, a follower shaft, and a transmission mechanism. The main body includes a housing and a drive shaft rotatably disposed in the housing in a way that the drive shaft is rotatable relative to the housing about a first axis. The extension arm includes a pivot portion rotatably connected with the housing of the main body in a way that the extension arm is rotatable relative to the housing about the first axis, a distal portion opposite to the pivot portion, and an internal accommodation penetrating through the pivot portion and the distal portion. The follower shaft is rotatably disposed in the distal portion in a way that the follower shaft is rotatable about a second axis that is parallel to and spaced from the first axis. The transmission mechanism is disposed in the internal accommodation of the extension arm and connected between the drive shaft and the follower shaft for transmitting a rotational power from the drive shaft to the follower shaft.

As a result, the handheld sander can fulfill different requirements of various working spaces because the extension arm of the handheld sander may have a relatively smaller thickness and can be rotated to various angles in accordance with the user's requirements. Compared to the conventional handheld sander, the handheld sander of the present invention can be operated in a limited, narrow working space to grind workpieces.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:

FIG. 1 is a perspective view of a handheld sander according to an embodiment of the present invention, showing an extension arm is in a non-rotated state;

FIGS. 2 to 4 are cutaway views showing parts of the handheld sander of the embodiment of the present invention;

FIG. 5 is a perspective view of a pivot portion of the extension arm of the embodiment of the present invention;

FIG. 6 is a perspective view showing a part of the handheld sander of the embodiment of the present invention; and

FIG. 7 is another perspective view of the handheld sander of the embodiment of the present invention, showing the extension arm is counterclockwise rotated at an angle of 90 degrees.

DETAILED DESCRIPTION OF THE INVENTION

Hereunder an embodiment will be detailedly described with accompanying drawings for illustrating technical features and structure of the present invention. As shown in FIGS. 1 to 6, a handheld sander 10 provided in accordance with an embodiment of the present invention comprises a handlebar 15, a main body 20, an extension arm 30, a follower shaft 40, a transmission mechanism 50, a first retaining member 60 moveably disposed with the main body 20, a second retaining member 70 moveably disposed with the extension arm 30, an abrasive disc 80 coaxially connected with the follower shaft 40, and a guard 90 rotatably disposed with the extension arm 30.

Referring to FIGS. 1 and 2, the maim body 20 includes a housing 22 and a drive shaft 24 rotatably disposed in the housing 22 in a way that the drive shaft 24 is drivenable by pneumatic power or electric motor to rotate relative to the housing 22 about a first axis A1 of the drive shaft 24. The housing 22 of the main body 20 includes a sleeve portion 221 of circular tubular shape, with which the first retaining member 60 is moveably disposed. Specifically, the sleeve portion 221 includes a first through hole 223, through which the first retaining member 60 extends. Further, a first resilient member 225 is disposed inside the first through hole 223 and abutted against the first retaining member 60. In the present embodiment, the handlebar 15 has an axial direction A, and the handlebar 15 is configured in a way that the handlebar 15 is rotatable relative to the main body 20 about the axial direction A at any desired angle, and the main body 20 is swivelable back and forth relative to the handlebar 15. In another feasible embodiment, the handlebar 15 is stationarily connected with the main body 20.

Referring to FIGS. 3 and 4, the extension arm 30 is configured as being rotatable about the first axis A1 relative to the housing 22. The extension arm 30 includes a pivot portion 32 rotatably connected inside the housing 22 of the main body 20, a distal portion 34 opposite to the pivot portion 32, an internal accommodation 36 penetrating from the pivot portion 32 to the distal portion 34, and a second through hole 38 communicated with the internal accommodation 36 and an outside of the extension arm 30 for the second retaining member 70 to pass therethrough. The pivot portion 32 of the extension arm 30 has a tubular shape, through which the drive shaft 24 extends into the internal accommodation 36. The sleeve portion 221 of the housing 22 is sleeved onto the pivot portion 32 of the extension arm 30. Further, the pivot portion 32 of the extension arm 30 includes an outer periphery, on which four positioning holes 321 are provided, as shown in FIG. 5. These positioning holes 321 are equiangularly arranged on the outer periphery of the pivot portion 32 at a ninety-degree interval in a way that the first retaining member 60 is selectively insertable into one of the positioning holes 321. Specifically speaking, the first resilient member 225 imparts a spring force on the first retaining member 60 toward the pivot portion 32 of the extension arm 30 to force the terminal end of the first resilient member 60 to contact the outer periphery of the pivot portion 32 and to be inserted into one of the positioning holes 321. Moreover, a second resilient member 381 is disposed in the second through hole 38 and abutted against the second retaining member 70 so as to impart a spring force on the second retaining member 70 toward a direction away from the internal accommodation 36. In another feasible embodiment, the pivot portion 32 may be provided with two or more positioning holes 321.

Referring to FIG. 6, both the follower shaft 40 and the guard 90 are rotatably disposed with the distal portion 34 in a way that both the follower shaft 40 and the guard 90 are rotatable about a second axis A2 of the follower shaft 40, which is parallel to and spaced from the first axis A1 at a predetermined distance. As shown in FIG. 6, a top section of the follower shaft 40 is connected with the transmission mechanism 50, and the bottom end of the follower shaft 40 is connected with a fastening unit 100, as shown in FIG. 3. In the present embodiment, the fastening unit 100 includes a clamping member 102 and a bolt 104 fastening the clamping member 102 to the follower shaft 40. The abrasive disc 80 is coaxially connected with the follower shaft 40 and fixedly sandwiched between the clamping member 102 and the follower shaft 40. In this way, when the follower shaft 40 rotates, the abrasive disc 80 will rotate along with the follower shaft 40. Under the condition that the abrasive disc 80 is fixed by the fastening unit 100, the abrasive disc 80 will not rotate or displace relative to the follower shaft 40 if no external force is applied on the abrasive disc 80. In another aspect, the guard 90 can be operated by the user to rotate to any desired angular position so as to block the processing debris or chip generated from grinding workpiece from hurting the user. In another feasible embodiment, the guard 90 can be provided stationarily, or the guard 90 can be omitted. Furthermore, the abrasive disc 80 may be replaced by other processing tools or bits.

The transmission mechanism 50 is disposed in the internal accommodation 36 of the extension arm 30 and connected between the drive shaft 24 and the follower shaft 40 for transmitting a rotational power of the drive shaft 24 to the follower shaft 40. In the present embodiment, the transmission mechanism 50 includes a first gear 52 coaxially connected with the drive shaft 24, a last gear 54 coaxially connected with the follower shaft 40, and two middle gears 56 located between the first gear 52 and the last gear 54 and meshed one with the other in a way that one of the middle gears 56 is meshed with the first gear 52 and the other middle gear 56 is meshed with the last gear 54. In other words, the first gear 52 is indirectly meshed with the last gear 54. The first gear52, the two middle gears 56, and the last gear 54 are all spur gears, thereby reducing transmission loss of the rotational power and enabling that the thickness of the extension arm 30 can be reduced because the spur gears require an installation space of lower height. Further, the transmission shaft 561 of one middle gear 56 is provided with a radial hole 563, into which the second retaining member 70 is optionally inserted. In another feasible embodiment, one or more middle gears 56 can be provided. Alternately, the middle gear 56 can be omitted, such that the first gear 52 is directly meshed with the last gear 54. Moreover, the first gear 52, last gear 54, and the middle gears 56 may be bevel gears, skew gears, etc. That is, they are not limited to spur gears.

In practical operation, when the user presses the switch button 151 on the handlebar 15, as shown in FIG. 1, the drive shaft 24 will be driven by a pneumatic power source or an electricity-powered driving source, such as electric motor, to rotate, and then the rotational power of the drive shaft 24 will be transmitted via the transmission mechanism 50 to the follower shaft 40, resulting in that the abrasive disc 80 is driven by the follower shaft 40 to rotate for grinding workpieces. In another aspect, if the handheld sander 10, which is set in a state that the extension arm 30 extends upwardly and is parallel to the axial direction A, as shown in FIG. 1, cannot work in a limited, narrower working environment to grind the workpieces, the user can operate the extension arm 30 to rotate about the first axis A1 to a proper angular position enabling the handheld sander 10 to work in the limited, narrower working environment so as to grind the workpieces. Hereunder an example showing the extension arm 30 is rotated at an angle of 90 degrees from the initial position, as shown in FIG. 7, will be given for illustrating the aforesaid angle-adjusting operation.

Since the first positioning member 60 receives a spring force from the first resilient member 225 toward the pivot portion 32, the terminal end of the first retaining member 60 is forced to be inserted into one of the positioning holes 321 to restrict the position of the pivot portion 32. In other words, the extension arm 30 cannot rotate about the first axis A1 relative to the housing 22 at this state. To rotate the extension arm 30, the user can pull outwardly the first retaining member 60 to disengage the terminal end of the first retaining member 60 from the associated positioning hole 321 so as to release the position restriction to the pivot portion 32, and then turn clockwise or counterclockwise the extension arm 30 about the first axis A1 to rotate relative to the housing 22. FIG. 7 is a schematic view showing the extension arm 30 has been turned counterclockwise at an angle of 90 degrees. During the process of turning the extension arm 30, the user needs not to continuously pull the first retaining member 60. Because the first retaining member 60 receives the spring force from the first resilient member 225, in the aforesaid turning period, the terminal end of the first retaining member 60 will be in contact with and slidably move along the outer periphery of the pivot portion 32 until the terminal end of the first retaining member 60 falls into the next positioning hole 321 as soon as the next positioning hole 321 is turned to a position in alignment with the terminal end of the first retaining member 60, thereby restricting the position of the pivot portion 32 again. In this way, the extension arm 30 will be unmovable relative to the housing 22 after the extension arm 30 is turned at an angle relative to the housing 22. In other words, the structure and shape (orientation angle) of the handheld sander 10 of the present invention can be adjusted in accordance with working requirements to enable the handheld sander 10 to work in a limited, narrow working space. It is to be understood that the more the positioning holes 321 on the pivot portion 32 are provided, the more the rotational angles of the extension arm 30 can get.

To replace the abrasive disc 80, for facilitating dismantlement of the fastening unit 100, the user can push with his/her finger of one hand the second retaining member 70 to force the terminal end of the second retaining member 70 to insert into the radial hole 563 of the transmission shaft 561 of the middle gear 56 to lock the transmission mechanism 50, thereby prohibiting the follower shaft 40 from rotation. As such, the user can use the other hand to dismantle the fastening unit 100 and then replace a new abrasive disc 80.

In the present invention, the extension arm 30 of the handheld sander 10 can be turned to one of various angles in accordance with working requirements. Further, because the thickness of the extension arm 30 is much thinner than that of the main body 20, and the extension arm 30 has a certain length, the extension arm 30 can be extended into a limited, narrow working space for grinding, thereby solving the problem that the conventional handheld sander may not be able to extend into a limited, narrow working space due to the thicker overall thickness of the conventional handheld sander resulted from the design that the abrasive disc of the conventional handheld sander is directly fixed to the drive shaft of the housing. In conclusion, the handheld sander 10 of the present invention is applicable in various working environments, especially in a limited, narrow working space, enhancing the convenience of usage.

Based on the above-mentioned technical features, various modifications to the structure of the handheld sander 10 may be made. For example, the way of restricting the position of the pivot portion 32 to prohibit the pivot portion 32 from rotation is not limited to the way described in the above-mentioned embodiment. As an exemplary embodiment, the pivot portion 32 may be configured as having no such positioning holes 321 on the outer periphery thereof, and the first retaining member 60 is realized as a bolt. By means of abutting the end of the bolt against the outer periphery of the pivot portion 32, the effect of prohibiting the pivot portion 32 from rotation can be achieved too. Alternately, the first retaining member 60 configured in a retractable and extendible manner can be provided at the outer periphery of the pivot portion 32, and the positioning holes 321 are provided at the inner periphery of the sleeve portion 221 for being inserted therein by the first retaining member 60. In other words, any way capable of restricting the position of the pivot portion 32 should be regarded as modification to the handheld sander 10 of the present invention. Further, in another feasible embodiment, the drive shaft 24 may be configured as not extending into the internal accommodation 36 and connect the first gear 52, but the transmission shaft of the first gear 52 is protruded out of the pivot portion 32 and connected with the drive shaft 24. Furthermore, the sleeve portion 221 may be provided at the extension arm 30, and the first through hole 223 is provided at the sleeve portion of the extension arm 30 for passing of the first retaining member 60 therethrough. Moreover, the radial hole 563 can be provided at the follower shaft 40 for being optionally inserted therein by the second retaining member 70. As such, when the second retaining member 70 is inserted into the radial hole of the follower shaft 40, the transmission mechanism 50 is prohibited from rotation. The transmission mechanism 50 may be configured having belts and wheels or chains for transmitting rotational power.

The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims. 

What is claimed is:
 1. A handheld sander, comprising: a main body including a housing and a drive shaft rotatably disposed in the housing in a way that the drive shaft is rotatable relative to the housing about a first axis; an extension arm including a pivot portion rotatably connected with the housing of the main body in a way that the extension arm is rotatable relative to the housing about the first axis, a distal portion opposite to the pivot portion, and an internal accommodation penetrating through the pivot portion and the distal portion; a follower shaft rotatably disposed in the distal portion in a way that the follower shaft is rotatable about a second axis that is parallel to and spaced from the first axis; and a transmission mechanism disposed in the internal accommodation of the extension arm and connected between the drive shaft and the follower shaft for transmitting a rotational power from the drive shaft to the follower shaft.
 2. The handheld sander as claimed in claim 1, wherein the pivot portion of the extension arm has a tubular shape, through which the drive shaft extends into the internal accommodation.
 3. The handheld sander as claimed in claim 1, wherein the housing of the main body comprises a sleeve portion sleeved onto the pivot portion of the extension arm.
 4. The handheld sander as claimed in claim 3, wherein the pivot portion of the extension arm includes an outer periphery, on which a plurality of positioning holes are provided; the handheld sander comprises a first retaining member moveably disposed with the sleeve portion of the housing in a way that the first retaining member is selectively inserted into one of the positioning holes.
 5. The handheld sander as claimed in claim 4, wherein the sleeve portion of the housing includes a first through hole, through which the first retaining member extends; a first resilient member is disposed inside the first through hole and abutted against the first retaining member for imparting a spring force on the first retaining member toward the pivot portion of the extension arm.
 6. The handheld sander as claimed in claim 1, wherein the transmission mechanism comprises a first gear coaxially connected with the drive shaft, and a last gear coaxially connected with the follower shaft; the first gear is directly or indirectly meshed with the last gear.
 7. The handheld sander as claimed in claim 6, wherein the first gear and the last gear are spur gears.
 8. The handheld sander as claimed in claim 6, wherein the transmission mechanism comprises a middle gear located between and meshed with the first gear and the last gear.
 9. The handheld sander as claimed in claim 6, wherein the transmission mechanism comprises a plurality of middle gears located between the first gear and the last gear and meshed one after another in a way that one of the middle gears is meshed with the first gear and another one of the middle gears is meshed with the last gear.
 10. The handheld sander as claimed in claim 8, wherein the first gear, the middle gear and the last gear are spur gears.
 11. The handheld sander as claimed in claim 8, wherein a transmission shaft of the middle gear or the follower shaft is provided with a radial hole; the handheld sander comprises a second retaining member moveably disposed with the extension arm and optionally inserted into the radial hole.
 12. The handheld sander as claimed in claim 11, wherein the extension arm includes a second through hole in communication with the internal accommodation and an outside of the extension arm; the second retaining member extends through the second through hole; a second resilient member is disposed in the second through hole and abutted against the second retaining member for imparting a spring force on the second retaining member toward a direction away from the internal accommodation.
 13. The handheld sander as claimed in claim 9, wherein the first gear, the middle gears and the last gear are spur gears.
 14. The handheld sander as claimed in claim 9, wherein a transmission shaft of one of the middle gears or the follower shaft is provided with a radial hole; the handheld sander comprises a second retaining member moveably disposed with the extension arm and optionally inserted into the radial hole.
 15. The handheld sander as claimed in claim 1, further comprising an abrasive disc coaxially connected with the follower shaft.
 16. The handheld sander as claimed in claim 1, further comprising a guard rotatably disposed on the distal portion of the extension arm in a way that the guard is rotatable about the second axis. 